{"cross_mech":[],"family":{"alphafold_models":526,"candidate_reasons":["pfam_previous_unknown_name"],"characterization_status":"","context_evidence_count":null,"cross_mech":{"example_proteins":0,"protein_traits_record":false,"records_by_mech":{},"scanned":false},"curation_status":"SEEDED","demotion_reasons":[],"description":"This entry represents ribosomal protein aS21, an archaea-specific component of the small ribosomal subunit (SSU). The protein was first characterised as HVO_2753 (Small CPxCG-related zinc finger protein) from Haloferax volcanii [[cite:PUB00096940]] and has been identified in ribosome structures from Pyrococcus abyssi [[cite:PUB00114374]] and Pyrobaculum calidifontis [[cite:PUB00161770]], where it is located at a position corresponding to eS21 in eukaryotic ribosomes. NMR 3D structure analysis revealed four C(P)XCG motifs, suggesting the presence of two zinc-binding pockets (ZBPs). While some members of this entry bind two zinc ions [[cite:PUB00161688]], in HVO_2753, only C(P)XCG motifs 2 and 4 (comprising Cys-32 to Cys-35 and Cys-50 to Cys-53) form a ZBP and bind one zinc atom, while C(P)XCG motifs 1 and 3 (comprising Cys-12 to Cys-15 and Cys-39 to Cys-42) form a four-Cys cluster that do not bind zinc. The four C(P)XCG motifs are critical for protein stability, folding and functionality [[cite:PUB00096940]]. Despite structural topology resembling eukaryotic eS21, sequence identities in the structurally superimposed regions are limited, and the archaeal protein contains two zinc knuckles not observed in the eukaryotic version [[cite:PUB00114374]]. The widespread conservation of this protein in archaeal genomes supports its role as a core ribosomal component [[cite:PUB00114374],[cite:PUB00161770]].","domain_architectures":1,"interpro_id":"IPR011668","known_evidence_count":null,"matches":557,"name":"Ribosomal protein aS21","partial_evidence_count":null,"pfam_id":"PF07754","proteins":557,"proteomes":551,"short_name":"Ribosomal_aS21","source_url":"https://www.ebi.ac.uk/interpro/api/entry/pfam/PF07754","structures":33,"taxa":1013,"unknown_status":"EX_DUF"},"inputs":{"cross_mech":"cross-mech-duf-examples-2026-10-10","members":"pfam-uniprot-uniref90-2026-10-07","protein_examples":"duf-protein-examples-2026-10-13","worklist":"interpro-pfam-duf-2026-10-10"},"members":[],"metadata":{"curation_status":"SEEDED","local_source":"source/data/families/PF07754.yaml","record":{"characterization_status":"UNSCORED","counters":{"alphafold_models":526,"domain_architectures":1,"matches":557,"proteins":557,"proteomes":551,"structures":33,"taxa":1013},"curation_status":"SEEDED","description":"This entry represents ribosomal protein aS21, an archaea-specific component of the small ribosomal subunit (SSU). The protein was first characterised as HVO_2753 (Small CPxCG-related zinc finger protein) from Haloferax volcanii [[cite:PUB00096940]] and has been identified in ribosome structures from Pyrococcus abyssi [[cite:PUB00114374]] and Pyrobaculum calidifontis [[cite:PUB00161770]], where it is located at a position corresponding to eS21 in eukaryotic ribosomes. NMR 3D structure analysis revealed four C(P)XCG motifs, suggesting the presence of two zinc-binding pockets (ZBPs). While some members of this entry bind two zinc ions [[cite:PUB00161688]], in HVO_2753, only C(P)XCG motifs 2 and 4 (comprising Cys-32 to Cys-35 and Cys-50 to Cys-53) form a ZBP and bind one zinc atom, while C(P)XCG motifs 1 and 3 (comprising Cys-12 to Cys-15 and Cys-39 to Cys-42) form a four-Cys cluster that do not bind zinc. The four C(P)XCG motifs are critical for protein stability, folding and functionality [[cite:PUB00096940]]. Despite structural topology resembling eukaryotic eS21, sequence identities in the structurally superimposed regions are limited, and the archaeal protein contains two zinc knuckles not observed in the eukaryotic version [[cite:PUB00114374]]. The widespread conservation of this protein in archaeal genomes supports its role as a core ribosomal component [[cite:PUB00114374],[cite:PUB00161770]].","id":"Pfam:PF07754","interpro_id":"InterPro:IPR011668","name":"Ribosomal protein aS21","pfam_id":"PF07754","provenance":{"generated_at":"2026-10-10T07:44:21.614711Z","path":"data/worklists/interpro-pfam-duf-2026-10-10.json","sha256":"17fb625876c9326ed284263a47bcd84e0d7844a31c040dc06cd2260c36f1c383","snapshot_id":"interpro-pfam-duf-2026-10-10","source_url":"https://www.ebi.ac.uk/interpro/api/entry/pfam/"},"seed_status":"EX_DUF","short_name":"Ribosomal_aS21","source_url":"https://www.ebi.ac.uk/interpro/api/entry/pfam/PF07754"},"source":{"commit":"c8155abfcf881ad8662936343deb81e604e3a194","path":"data/families/PF07754.yaml","repository":"https://github.com/CultureBotAI/DUFMech","sha256":"89df7d1c6a1104f89c002ceb9d04f424ddf388920e456a3f57c82a504ebe9bf5"}},"protein_examples":{"candidate_count":1,"discovery_scanned":true,"example_count":1,"examples":[{"evidence_scope":"FAMILY_MEMBERSHIP_NOT_FUNCTION","organism":"Methanocaldococcus jannaschii (strain ATCC 43067 / DSM 2661 / JAL-1 / JCM 10045 / NBRC 100440)","origins":[{"cited_uniprot_accession":"","commit":"70edd6f8458845f7d7783ac4f416df519f5e1de6","link_basis":["canonical_example_family_classification"],"mech":"ProteinTraitsMech","path":"data/traits/function/protein_family/ncbifam/putative-zn-ribbon-rna-binding-protein-nf011481.yaml","qualification_status":"NOT_ASSESSED","record_id":"NCBIfam:NF011481","section":"canonical_examples","url":"https://github.com/CultureBotAI/proteintraitsmech/blob/70edd6f8458845f7d7783ac4f416df519f5e1de6/data/traits/function/protein_family/ncbifam/putative-zn-ribbon-rna-binding-protein-nf011481.yaml"},{"cited_uniprot_accession":"","commit":"70edd6f8458845f7d7783ac4f416df519f5e1de6","link_basis":["canonical_example_family_classification"],"mech":"ProteinTraitsMech","path":"data/traits/sequence/domain/interpro/ribosomal-protein-as21-zinc-binding-pocket-ipr011668.yaml","qualification_status":"NOT_ASSESSED","record_id":"InterPro:IPR011668","section":"canonical_examples","url":"https://github.com/CultureBotAI/proteintraitsmech/blob/70edd6f8458845f7d7783ac4f416df519f5e1de6/data/traits/sequence/domain/interpro/ribosomal-protein-as21-zinc-binding-pocket-ipr011668.yaml"},{"cited_uniprot_accession":"","commit":"70edd6f8458845f7d7783ac4f416df519f5e1de6","link_basis":["canonical_example_family_classification","ptm_own_pfam_record_example"],"mech":"ProteinTraitsMech","path":"data/traits/sequence/domain/pfam/ribosomal-as21-pf07754.yaml","qualification_status":"LEGACY_OR_UNSPECIFIED","record_id":"Pfam:PF07754","section":"canonical_examples","url":"https://github.com/CultureBotAI/proteintraitsmech/blob/70edd6f8458845f7d7783ac4f416df519f5e1de6/data/traits/sequence/domain/pfam/ribosomal-as21-pf07754.yaml"},{"cited_uniprot_accession":"","commit":"70edd6f8458845f7d7783ac4f416df519f5e1de6","link_basis":["ptm_registry_exact_uniprot_pfam_xref"],"mech":"ProteinTraitsMech","path":"data/grounding/protein_registry.jsonl","qualification_status":"NOT_ASSESSED_FOR_THIS_FAMILY","record_id":"UniProtKB:P81308","section":"protein_registry","url":"https://github.com/CultureBotAI/proteintraitsmech/blob/70edd6f8458845f7d7783ac4f416df519f5e1de6/data/grounding/protein_registry.jsonl"}],"pfam_ids":["PF07754"],"protein_name":"Small ribosomal subunit protein aS21","registry_source":{"commit":"70edd6f8458845f7d7783ac4f416df519f5e1de6","path":"data/grounding/protein_registry.jsonl","repository":"https://github.com/CultureBotAI/proteintraitsmech","sequence_sha256":"35675b0b6d92d421236fc2b465577793447d8e8a6ac0a365d024ffa68d50b60c","sequence_version":1,"sha256":"1be0cf02b76b03a8fe9b80bcead9cd4a419157116eb8da038f266bcc33015eb9","uniprot_release":"2026_03","url":"https://github.com/CultureBotAI/proteintraitsmech/blob/70edd6f8458845f7d7783ac4f416df519f5e1de6/data/grounding/protein_registry.jsonl"},"registry_status":"EXACT_SEQUENCE_VERSION_MATCH","reviewed":true,"sequence":"MGEMKYVCISCNAEIAPREKSTKFPCPNCGEVEIVRCERCRKLNNPYKCPKCGFEGP","sequence_length":57,"sequence_origin":"PTM_REGISTRY_MIRROR","sequence_sha256":"35675b0b6d92d421236fc2b465577793447d8e8a6ac0a365d024ffa68d50b60c","sequence_version":1,"source_url":"https://rest.uniprot.org/uniprotkb/P81308.json","taxon_id":"243232","uniprot_accession":"P81308","uniprot_release":"2026_03"}],"pfam_id":"PF07754","short_name":"Ribosomal_aS21","status":"HAS_SEQUENCE_EXAMPLE","unresolved":[]}}